Altera Cyclone II FPGA Starter Development Board - Manual (Page 34)

2–16 Reference Manual Altera Corporation
Cyclone II FPGA Starter Development Board October 2006
Development Board Components
Additionally, with the switch in the RUN position, the Quartus II
Programmer can program the FPGA directly through the USB Blaster
circuit. With the switch in the PROG position, the Quartus II Programmer
can program the EPCS4 device.
Push Button Switches
The development board provides four push button switches,
KEY0-KEY3
, located at the bottom right on the development board below
the green LEDs, LEDG0-LEDG7 ( Figure 2–10 ). The momentary-contact
switches provide stimulus to designs in the FPGA.
Figure 2–10. Push Button Switches and Green LEDs
A switch generates an active-LOW pulse at 0 volts when pressed,
returning to a HIGH logic level at 3.3 volts when released. A Schmitt
Trigger circuit on each switch debounces the signal (
Figure 2–11 ).
Figure 2–11. Switch Debouncing